We propose to further study the physiology of receptors which may not be regulated receptors. As we have demonstrated, receptors involved in ligand uptake may not be affected by previous exposure to ligand in terms of a reduction in receptor number or activity. continued ligand uptake may result in such activities as macrophage protease secretion. Studies are in progress examining what receptors on the macrophage surface exhibit unregulated receptor. Additionally, we are also examining if the transferring receptor on cultured fibroglass also exhibit unregulated receptor activity. In particular is iron uptake regulated, and if so is the locus of regulation subsequent to ligand-receptor interactions.